seaport, Ille-et-Vilaine département, Brittany région, northwestern France. It is situated on the English Channel and on the right bank of the estuary of the Rance River. The old walled city stands on a granite islet that is joined to the mainland by an ancient causeway and by an avenue bridging the inner harbour.

Saint-Malo was named for Maclou, or Malo, a Welsh monk who fled to Brittany, making his headquarters on the island, in the 6th century and probably became the first bishop of Aleth (Saint-Servan). The island was not substantially inhabited until the 8th century, when the population of the surrounding district sought refuge there from the Normans. The bishopric was transferred to the island in 1144 and was abolished in 1790. In the 17th and 18th centuries, Saint-Malo derived prosperity from its navigators, traders, and privateers. The town was three-fourths destroyed during World War II, but it has been rebuilt.

The fortress at the northeast corner of the ramparts, built between the 14th and the 17th century, has four great round towers, one of which houses a museum devoted largely to famous mariners born in the city, including the 16th-century French navigator Jacques Cartier (Cartier, Jacques). The 12th–17th-century Church of Saint-Vincent, previously the cathedral, was damaged in World War II but has undergone restoration work.

Various activities are linked to the town's port, part of which is a yachting harbour. Freight and passenger ferries connect Saint-Malo to England, Ireland, and the Channel Islands. Saint-Malo's industries include food processing (shellfish), shipbuilding, and the manufacture of machinery and chemicals. The world's first large-scale tidal plant, using flood and ebb tides to generate electricity, was completed in Saint-Malo in 1967. Pop. (1999) 50,675; (2005 est.) 49,600.